Method of deburring a flat workpiece



April l, 1959 J. ENSERINK 3,435,566

METHOD OF DEBURRING A FLAT WORKPIECE Filed Nov. so. 1964 INVENTOR ZTHN ENSERNK ATTORNEYS United States Patent U.S. Cl. 51-328 2 Claims ABSTRACT OF THE DISCLOSURE `Employing a grinding wheel of resilient material having abrasive particles of predetermined size for removing burrs on a flat workpiece without any substantial grinding effect upon the surface of the workpiece between burrs by adjusting the peripheral speed of the grinding wheel in accord with the abrasive particle size.

Background of invention According to conventional methods, some of the surface of a workpiece may possibly be removed together with the burrs and the latter may in fact not even be completely removed. Whether or not all the burrs are removed depends on the grinding intensity so that material may also be removed from the surface of the workpiece or else the deburring operation may be unsatisfactory.

Summary of invention The invention provides a method whereby the workpiece can be thoroughly deburred without ldamage to the surface of the workpiece, this being very important, particularly in the case of a sheet or plate having a thin corrosion-resistant or anti-corrosion coating.

To this end, in the method according to the invention, a grinding wheel consisting of grains of a certain size bonded with porous rubber is used and the circumferential speed of the grinding wheel is adjusted in accordance with the grain size. Tests have shown that for a specic grinding speed the abrasive grains bonded in porous rubber attack the burrs but do not or substantially do not attack the at surface in front of and after the burr.

'Excellent results were obtained in the `deburring of dural `sheets with a 0.04 mm. anti-corrosion aluminium coating, using a grinding wheel consisting of aluminium oxide grains, more particularly grains of a size of 120 mesh, while the grinding wheel was driven at a circumferential speed of about 12 metres per second in the same direction as the direction of movement of the workpiece. The speed of the latter with respect to the grinding wheel was 0.5-2.5 metres per minute and the pressure about 0.6 kg. per centimetre of wheel length.

The grinding wheel is driven at its periphery by a driving wheel at a circumferential speed of about 12 metres per second so that the speed of grinding is not affected by the grinding wheel wear.

In a further development of the device according to the invention, the grinding wheel material consists of grains bonded with solid rubber and the grinding wheel grains and the driving wheel grains are of the same material. The driving wheel wear is low so that the circumferential speed does not or at least does not appreciably vary.

Brief description of the drawing Features of the invention will be explained hereinbelow with reference to the drawing, wherein:

FIG. 1 is a diagrammatic partial longitudinal section of 3,435,566 Patented Apr. 1, 1969 lCe a sheet and grinding wheel during the deburring operation.

FIG. 2 is a cross-section on the line II--Il in FIG. l. FIG. 3 is a side elevation of a device according to the mvention.

FIG. 4 is a partial cross-section on the line IV--IV in FIG. 3.

FIG. 5 is a similar view to PIG. 3 but shows a grinding wheel worn to an increased degree.

Detailed description of invention As already stated, the object of the invention is to remove the burrs 1 which form when a plate 3 is machined with apertures 2 for example, a grinding wheel 4 being used to remove the burrs without the grinding wheel attacking the thin corrosion-resistant or anti-corrosion coating 5 at the surface of the plate 3. In aircraft construction, frequent use is made of sheetmetal consisting of Al-C'u and Al-Zn alloy coated with an anti-corrosion coating of pure aluminium in a thickness of, for example, 0.04 mm.

Such sheets can be satisfactorily deburred by means o'f a device as shown in FIG. 3, which consists essentially of a frame 6, a conveyor belt 7, a grinding wheel 4, a driving wheel 8, and a yoke 9 rockable about a shaft 10. The shaft 11 of the grinding wheel 4 is transversely slidable, FIG. 4, in a bearing 13- in each of the two side walls 12 of the yoke 9.

The ydriving wheel 8 is also mounted in each of the two side walls 12 of the yoke 9 and is movable in slots 14 so that it can follow the grinding wheel 4 as the diameter of the latter decreases. The drive wheel 8 is driven by the shaft 10 via a belt transmission 15 and is pressed resiliently against the outside of the grinding wheel 4 so that wear of the latter has no influence on the grinding speed.

The yoke 9 is so balanced that the grinding wheel 4 bears on the workpiece with a low force (0.6 kg. per cm. of Wheel length). The shaft 10 is `disposed as close as possible to the grinding surface or the top surface of the conveyor belt to minimize variations in the pressure of the grinding wheel l4 on the workpiece by reducing the moment due to the tangential load imposed upon the grinding wheel incidental to the grinding operation. The height of the grinding wheel 4 above the conveyor belt 7 is adkjustable by adjustment of a spindle 16. The vertical adjustment is satisfactory when the grinding wheel 4 just touches the surface of the workpiece. I'f the grinding wheel 4 is set too low, the side edge of the workpiece will be excessively rounded. A spring 17 is provided in this mechanism to allow the yoke `9 to pivot without any impacts.

Spring-loaded pressure rollers 18, 19 and 20 ensure good Contact between the workpiece 3 to be deburred and the conveyor belt, which may be provided with a nap pattern. The rollers 19 and 20 hol-d the workpiece rigidly during the deburring operation and the roller 20 in particular prevents the workpiece from being ejected from the device at excessive speed. The distance between the rollers 19 and 20 limits the minimum length of workpieces which may be handled, it being necessary that the workpiece be engaged by at least one of the rollers at all times. The rollers 19 and 20 are therefore disposed as close as possible at the grinding wheel 4.

The yoke 9 includes a large hood around the rollers and wheels and is connected by a hose 21 to a suction extraction unit to remove the abraded material. A flexible ap 22 shuts oft the underside of the box.

To ensure uniform wear of the grinding wheel 4, the latter reciprocates transversely (see arrows in FIG. 4), for example by means of a crank and connecting rod mechanism. If the grinding wheel 4 nevertheless wears unevenly,

such unevenness may lbe obviated by moving a scraper or such like rubber removing apparatus (not shown) in parallel relationship to the shaft of the rotating grinding wheel 4.

The abrasive grains of the grinding wheel 4 are bonded with porous rubber primarily to prevent any foreign metal from remaining on the workpiece.

A specific grain size is also selected and a test or a number of tests carried out to determine the grinding speed to ensure that although the burrs of a testpiece are ground away the surface of the workpiece is not attacked or substantially not attacked, this being very important in the case of clad metals. If the test workpiece is coated with an etching agent or some other indicating liquid, it is easy to tell whether the clad coating has been ground away -during the treatment. Once the grinding speed required for a specific grain size has been determined, all the sheet-metal material of the same type can be satisfactorily deburredwith the appropriate grinding wheel 4 under the same conditions. Of course, no tests are required if the preferential grinding speed, grain size and other conditions mentioned in this description are applied. FIG. 2 shows on an exaggerated scale how the surface of the grinding wheel is deformed in the transverse direction. The grinding wheel 4 touches the sheet 3 just at the edges where the burrs 1 are situated. In the longitudinal direction or the direction of grinding the said required grinding speed in conjunction with the selected pressure and grinding wheel prevents the abrasive grains which meet the burrs 1 and which may or may not become detached, from excessively grinding away the top surface 5 of the sheet 3.

The speed of the conveyor belt 7 is infinitely variable preferably from a speed of 2.505 metres per minute. Where large burrs have to be removed, a low speed is selected for the conveyor belt 7, while the high speed is used for small burrs.

The grinding wheel 4, which is composed of a number I of discs disposed on the shaft 11, is interchangeable and is disposed between two shaft ends by means of a pull-rod 24.

Each of the bearings 13 is protected from abraded dust by a dust seal 26.

What I claim is:

1. The method of deburring a ilat workpiece, having a .f

outstanding to remove the workpiece burrs without any substantial abrasive eifect on the Surface of the workpiece between burrs,

said grinding wheel having a hardness of about Shore and grains of a grain size of about 120 mesh, the workpiece being moved at a speed of 0.5-2.5 meters per minute past the grinding wheel, the latter being pressed against the workpiece at a force of about 0.6 kg. per centimeter of wheel length and the grinding wheel being driven at a circumferential speed of about l2 meters per second in the same direction as the direction of movement of the workpiece.

2. The method of deburring a at workpiece, having a hat surface from which a plurality of spaced, outstanding burrs project, which comprises,

`feeding the workpiece at a predetermined linear speed along a given path,

contacting a resilient grinding wheel against the workpiece as it is fed along said given path, the grinding wheel having abrasive grains of a predetermined size,

and adjusting the peripheral speed of said grinding wheel in accord with the size of said abrasive grains so as to remove the workpiece burrs without any substantial abrasive effect on the surface of the workpiece between burrs,

said grinding wheel being of 85 Shore hardness and driven by a driving wheel of a hardness of Shore with grains of a grain size of about and 60 mesh respectively for the grinding and `driving wheels, the lworkpiece being driven at a speed of 0.5-2.5 meters per minute, the force at which the grinding wheel is pressed against the workpiece being adjustable to about 0.6 kg. per centimeter of wheel length and the driving wheel being driven at a circumferential speed of about l2 meters per second.

References Cited UNITED STATES PATENTS 1,446,654 2/1923 Northrup 51-78 1,915,323 6/1933 Lane g 51--34.7 1,976,114 10/1934 Booth 51-34.7 2,340,121 1/1944 Hamilton 51--78 2,537,394 1/1951 Boice 51-134.5 2,986,455 5/1961 Sandmeyer 5`1--299 X 3,277,609 10/ 1966 Horie 51-78 LESTER M. SWINGLE, Primary Examiner.

D. G. KELLY, Assistant vExamz'ner.

U.S. Cl. X.R. 51-38, 76, 358 

